Plants would not be able to fill the atmosphere with oxygen if not for the symbiosis with fungi, which have provided them with phosphorus and other minerals for hundreds of millions of years.
The Earth's modern atmosphere is created by life: photosynthetic organisms have filled it with oxygen and removed carbon dioxide. However, billions of years before that, this was not at all the case. The atmosphere of a young planet would be toxic to us, full of carbon dioxide, methane and hydrogen sulfide. Enough oxygen began to accumulate in the air only after the appearance of land plants - 500–400 million years ago.
However, modern plants photosynthesize by extracting minerals from the soil using the root system and distributing it using the conducting system. The first land plants did not have either one or the other, and there was still no soil saturated with soluble salts. They could not even get ordinary phosphorus, which is absolutely necessary for photosynthesis.
“Photosynthesis of land plants creates about half of all the oxygen on earth,” explains Benjamin Mills of the University of Leeds. "And this process requires phosphorus, although we still have little understanding of how the global circulation of this substance works."
In an article published in the journal Philosophical Transactions B, Mills and colleagues suggest that even the first plants could only colonize the land in symbiosis with fungi. By giving them part of their synthesized organic matter, they received in return minerals that many mushrooms are able to dissolve.
To confirm their hypothesis, scientists conducted experiments showing that modern representatives of ancient lines of fungi really provide plants with an influx of minerals, the intensity of which determines the intensity of photosynthesis and oxygen release.
The same was indicated by computer modeling of the Paleozoic climate. The work showed that the rate of exchange of carbon and minerals between plants and fungi significantly influenced the climate of the whole planet - by changing the rate of absorption of carbon dioxide and the release of free oxygen.
Sergey Vasiliev
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